1. Field of the Invention
This invention relates to a picture data generating method and apparatus for processing data of a string of parallax images composed of plural pictures containing the parallax information with parallax conversion to generate data of a new string of parallax images.
2. Description of the Related Art
A holographic stereogram is prepared by sequentially recording a large number of pictures, as original image, obtained on sequentially imaging an object from plural viewing points, on a sole recording medium for hologram as strip-shaped or dot-shaped elementary holograms.
For producing a holographic stereogram having the parallax information only in the horizontal direction, an object 100 is imaged sequentially from different viewing points in the horizontal direction to produce a string of parallax images 101 which is made up of plural images 102 having the parallax information in the horizontal direction. The images 102 making up this string of parallax images 101 are sequentially recorded as strip-shaped elementary holograms on a hologram recording medium 103 so that the images will be contiguous to one another in the horizontal direction. This gives a holographic stereogram having the parallax information in the horizontal direction.
With this holographic stereogram, the information of plural images 102, obtained on sequentially imaging from different viewing points arrayed in the horizontal direction, is sequentially recorded as strip-shaped elementary holograms in a horizontally contiguous row of images. Thus, if a viewer observes the holographic stereogram with both eyes, the two-dimensional pictures as seen by the left and right eyes differ slightly from each other because of the slight difference in the positions of the left and right eyes in the horizontal direction. Thus, the viewer feels the parallax, with the reproduced picture being recognized as a three-dimensional picture.
The string of parallax images, from which the holographic stereogram is produced, is obtained on horizontally translating a camera 104, oriented towards the object 100, with its orientation being kept unchanged, and imaging the object 100 a number of times from different positions. That is, the camera 104, oriented towards the object 100, is translated, from a position in which the object 100 begins to be captured by the camera 104 up to a position in which the object 100 ceases to be captured by the camera 104, and a number of images are shot during this time interval, whereby the string of parallax images, form which the holographic stereogram is derived, is obtained. Meanwhile, this system of translating the camera 104, with the orientation of the camera 104 remaining fixed, and imaging the object 100 a number of times from different positions, is termed a straight track system.
It is noted that, in the holographic stereogram, the relative position between the viewing point of the camera 104 and the object 100 during imaging is kept in the reproduced images of the produced holographic stereogram. Thus, if the string of the parallax images, produced as described above, is directly used for preparation of the holographic stereogram, a reproduced image Z is formed at a recessed position as from a hologram surface Ha of a holographic stereogram 100, as shown in FIG. 3. Thus, in such holographic stereogram H, the reproduced image Z is distorted or blurred, unless the reproduced image is viewed with the viewing point S set on the hologram surface Ha, so that a distance do between the reproduced image Z and the viewing point S of the viewer coincides with a distance d between the object 100 being imaged and the viewing point of the camera 104.
Therefore, if, in producing the holographic stereogram, the above-mentioned problem is to be solved, it is necessary to process data of the original string of parallax images with viewing point conversion so that the reproduced image Z will be imaged in the vicinity of the hologram surface Ha of the holographic stereogram 100. By this viewing point conversion processing, the reproduced image Z free of distortion or blurring can be produced even if the viewing point S is spaced apart from the hologram surface Ha.
In preparing the holographic stereogram, it is necessary to execute the above-described viewing point conversion processing, which, however, requires a complex arithmetic operations. For this reason, preparation of the holographic stereogram is time-consuming. That is, the operation of processing the data of the string of the parallax images with viewing point conversion to produce new data of the string of the parallax images is time-consuming such that a holographic stereogram cannot be prepared promptly.
However, if the holographic stereogram producing system is to be practically used as a printer device for outputting a hard copy from which a three-dimensional image can be prepared, the time as from the inputting of images as a source of the holographic stereogram until completion of the holographic stereogram needs to be shortened. That is, expedited viewing point conversion processing is desired strongly.
The viewing point conversion processing is desired to be expedited in other processes than the above-described process for preparing the holographic stereogram. For example, there are occasions wherein the viewing point conversion processing is carried out for displaying a stereoscopic image on a display device by exploiting the parallax. It goes without saying that, in such case, the viewing point conversion processing is desirably carried out expeditiously.
It is therefore an object of the present invention to provide an image data generating method and apparatus whereby, in processing data of the parallax image string made up of plural images carrying the parallax information with viewing point conversion processing to generate data of a new parallax image string, these data of the new parallax image string can be generated expeditiously.
In one aspect, the present invention provides an image data generating apparatus in which viewing point conversion processing is performed on data of a first string of parallax images made up of plural images containing the parallax information to generate data of a second string of parallax images. The apparatus includes lookup table storage means for storing a lookup table giving the relation of correspondence between pixels of a first string of parallax images and those of a second string of parallax images. The data of the second string of parallax images from data of the first string of parallax images are generated by performing the viewing point conversion processing by pixel interchanging based on the lookup table stored in the lookup table storage means.
In the viewing point conversion processing general, the relation of correspondence between pixels of a first string of parallax images and those of a second string of parallax images is constant at all times if the parameters for the viewing point conversion processing are constant. Therefore, if the relation of correspondence is previously known, the viewing point conversion processing may be realized simply by pixel interchanging which is based on the above relation of correspondence.
In the image data generating apparatus, the viewing point conversion processing can be realized promptly without the necessity of executing complex arithmetic processing operations.
The image data generating apparatus preferably includes image data storage means for storing data of a string of parallax images. When generating data of the second string of parallax images, data of respective images making up the string of parallax images are sequentially stored in the image data storage means, and the viewing point conversion processing is effectuated after storing the entire data of the string of parallax images into the image data storage means. This renders it possible to input the string of parallax images to the apparatus in real-time each time an image of the string of parallax images is shot.
The image data generating apparatus preferably includes lookup table generating means for generating the lookup table by finding the relation of correspondence between pixels of the original string of parallax images and those of a new string of parallax images.
In the image data generating apparatus, preferably the lookup table storage means is of an overwrite type and is adapted to rewrite the contents of the lookup table responsive to the desired viewing point conversion processing since this enables a variety of types of the viewing point conversion processing with different parameters to be coped with.
If, in the image data generating apparatus, the string of parallax images has parallax only in one direction, preferably the relation of correspondence between pixels of the images making up the string of parallax images and those making up the new string of parallax images is recorded in the lookup table, with a pixel line made up of a line of plural pixels as a minimum unit. When carrying out the viewing point conversion processing, pixel interchanging is effectuated with the pixel line as a minimum unit.
If the pixels are interchanged with the pixel line as a minimum unit, the pixel line corresponds to a scanning line for displaying the image on a display device. If the string of parallax images has parallax only in the scanning line direction, the viewing point conversion processing is effectuated on rotating the images making up the string of parallax images by 90xc2x0.
If, in the above image data processing apparatus, keystone distortion is produced in the original string of parallax images, correction parameters for correcting the keystone distortion are preferably contained in the lookup table in addition to the it relation of correspondence between pixels of the images making up the string of parallax images and those making up the new string of parallax images. When effectuating the viewing point conversion processing, pixel interchanging is effectuated based on the lookup table, while the keystone distortion is corrected based on the correction parameters.
In the above image data processing apparatus, the data of a newly generated string of parallax images is data of a string of parallax images recorded on a holographic stereogram, and the images making up the string of parallax images is recorded as elementary holograms making up the holographic stereogram.
If data of a string of parallax images newly generated by the image data generating apparatus are data of a string of parallax images to be recorded on a holographic stereogram, data of the string of parallax images subjected to viewing point conversion processing is sequentially outputted in a timed relation to the recording of each elementary hologram in terms of an image of the string of parallax images as a unit. This enables the holographic stereogram to be prepared promptly.
In another aspect, the present invention provides an image data processing method in which viewing point conversion processing is performed on data of a the string of parallax images made up of plural images containing the parallax information to generate data of a new string of parallax images. The image data processing method includes producing a lookup table giving the relation of correspondence between pixels of a the string of parallax images and those of the new string of parallax images, and generating data of the new string of parallax images from data of the string of parallax images by performing the viewing point conversion processing by pixel interchanging based on the lookup table.
This renders it possible to execute the viewing point conversion processing expeditiously without requiring complex arithmetic operations.
In the image data processing method, when generating data of the new string of parallax images, data of respective images making up the string of parallax images are sequentially stored in image data storage means, and the viewing point conversion processing is effectuated after storing the entire data of the string of parallax images into the image data storage means. This renders it possible to input the string of parallax images to the apparatus in real-time each time an image of the string of parallax images is shot.
In the image data processing method, the lookup table is stored in an overwrite memory and, before proceeding to viewing point conversion processing, the contents of the lookup table are preferably rewritten responsive to the desired viewing point conversion processing, since this enables a variety of types of the viewing point conversion processing with different parameters to be coped with.
If the string of parallax images has parallax only in one direction, the relation of correspondence between pixels of the images making up the string of parallax images and those making up the new string of parallax images is preferably recorded in the lookup table with a pixel line made up of a line of plural pixels as a minimum unit. Also, when effectuating the viewing point conversion processing, pixel interchanging is effectuated with the pixel line as a minimum unit. This assures more efficient viewing point conversion processing.
In case of effectuating the pixel interchanging with the pixel line as a minimum unit, the pixel line preferably corresponds to a scanning line for displaying the image on a display device. If the string of parallax images has parallax only in the scanning line direction, the viewing point conversion processing is effectuated on rotating the images making up the string of parallax images by 90xc2x0.
If, in the image data processing method, there is produced keystone distortion in the original string of parallax images, correction parameters for correcting the keystone distortion are preferably contained in the lookup table in addition to the relation of correspondence between pixels of the images making up the string of parallax images and those making up the new string of parallax images. When effectuating the viewing point conversion processing, pixel interchanging is effectuated based on the lookup table, while the keystone distortion is corrected based on the correction parameters. This gives data of the string of parallax images corrected for the keystone distortion.
The data of the new string of parallax images is data of a string of parallax images recorded on a holographic stereogram, and the images making up the string of parallax images are recorded as elementary holograms making up the holographic stereogram.
If the data of the new string of parallax images generated by the image data generating method is data of a string of parallax images recorded on a holographic stereogram, data of the string of parallax images subjected to viewing point conversion processing is sequentially outputted in a timed relation to the recording of each elementary hologram in terms of an image of the string of parallax images as a unit.
According to the present invention, data of a new string of parallax images can be generated expeditiously by performing viewing point conversion processing on data of a string of parallax images made up of plural images containing the parallax information. Thus, a holographic stereogram, for example, can be prepared expeditiously.